//位字段和按位运算符
#include<stdio.h>
#include<stdbool.h>
#include<limits.h>

/*位字段符号常量*/
//边框线样式
#define SOLID  0
#define DOTTED 1
#define DASHED 2
//三原色
#define BLUE  4
#define GREEN 2
#define RED   1
//混合颜色
#define BLACK   0
#define YELLOW  (RED | GREEN)
#define MAGENTA (RED | BLUE)
#define CYAN    (GREEN | BLUE)
#define WHITE   (RED | GREEN | BLUE)
/*按位方法中用到的符号常量*/
#define OPAQUE       0X1
#define FILL_BLUE    0X8
#define FILL_GREEN   0X4
#define FILL_RED     0X2
#define FILL_MASK    0XE
#define BORDER       0X100
#define BORDER_BLUE  0X800
#define BORDER_GREEN 0X400
#define BORDER_RED   0X200
#define BORDER_MASK  0XE00
#define B_SOLID      0
#define B_DOTTED     0X1000
#define B_DASHED     0X2000
#define STYLE_MASK   0X3000

const char * colors[8] = {"black", "red", "green", "yellow", "blue", "magenta", "cyan", "white"};

struct box_props{
    bool opaque : 1;
    unsigned int fill_color : 3;
    unsigned int : 4;
    bool show_border : 1;
    unsigned int border_color : 3;
    unsigned int border_style : 2;
    unsigned int : 2;
};

//把数据看作 结构 或 unsigned short 类型的变量
union Views{  
    struct box_props st_view;
    unsigned short us_view;
};

void show_settings(const struct box_props * pb);
void show_settings1(unsigned short);
char * itobs(int n, char * ps);

int main(void)
{
    //用一个成员把值存在联合中，用另外一个成员查看内容
    union Views box = { {true, YELLOW, true, GREEN, DASHED} };
    char bin_str[8 * sizeof(unsigned int) + 1];

    printf("Original box settings:\n");
    show_settings(&box.st_view);
    printf("\nBox settings using unsigned int view:\n");
    show_settings1(box.us_view);

    printf("bits are %s\n", itobs(box.us_view, bin_str));
    box.us_view &= ~FILL_MASK;  //把表示填充色的位清0
    box.us_view |= (FILL_BLUE | FILL_GREEN);
    box.us_view ^= OPAQUE;
    box.us_view |= BORDER_RED;  //错误方法（没有清空）
    box.us_view &= ~STYLE_MASK;  //把样式的位清0
    box.us_view |= B_DOTTED;
    printf("\nModified box settings:\n");
    show_settings(&box.st_view);
    printf("\nBox settings using unsigned int view:\n");
    show_settings1(box.us_view);
    printf("bits are %s\n", itobs(box.us_view, bin_str));

    return 0;
}

void show_settings(const struct box_props * pb)
{
    printf("Box is %s.\n",
        pb->opaque == true ? "opaque" : "transparent");
    printf("The fill color is %s.\n", colors[pb->fill_color]);
    printf("Border %s.\n",
        pb->show_border == true ? "shown" : "not shown");
    printf("The border color is %s.\n", colors[pb->border_color]);
    printf("The border style is ");
    switch (pb->border_style)
    {
        case SOLID: printf("solid.\n"); 
            break;
        case DOTTED: printf("dotted.\n");
            break;
        case DASHED: printf("dashed.\n");
            break;
        default: printf("unknown type.\n");
    }
}

void show_settings1(unsigned short us)
{
    printf("box is %s.\n",
        (us & OPAQUE) == OPAQUE ? "opaque" : "transparent");
    printf("The fill color is %s.\n",
        colors[(us >> 1) & 07]);
    printf("Border %s.\n",
        (us & BORDER) == BORDER ? "shown" : "not shown");
    printf("The border style is ");
    switch(us & STYLE_MASK)
    {
        case B_SOLID: printf("solid.\n");
            break;
        case B_DOTTED: printf("dotted.\n");
            break;
        case B_DASHED: printf("dashed.\n");
            break;
        default: printf("unknown type.\n");
    }
    printf("The border color is %s.\n",
        colors[(us >> 9) & 07]);
}

char * itobs(int n, char * ps)
{
    int i;
    const static int size = CHAR_BIT * sizeof(int);

    for(i=size-1; i>=0; i--, n>>=1)
        ps[i] = (01 & n) + '0';
    ps[size] = '\0';
    return ps;
}